Yes, I bought a 1320 overpipe too ( 60mm version ) and I haven't gas leaks using stock frontpipe.
I replaced only engine to header gaskets and headers to overpipe gasket.
O2 sensor "L" extension works well, no one CEL from installation made 15 days ago and about 1000km ( 600km highways, suburban 340km , 60km urban ) always using 100RON premium unleaded fuel
and stock firmware ZA1JA02G ( not yet tuned )
Sure ? I ordered mine while "out of stock" and they have been delivered in 6 days, and I live in Italy!
Here you can find a couple of video, first is a cold start and second one an hill road test.
Keep in mind, I've changes ONLY headers and overpipe, while frontpipe-midpipe-muffler are stock ( and not TDR or STI version ), i'm only search for a bit more "Subaru rumble" sound
and torque gain in 3500-4500 for my daily car.
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